if the UDP you get is good quality and balanced from factory then i don't think that you will feel any vibrations. the people that have vibration issues are probably getting cheap pulleys that aren't balanced. you will still have the torsional vibrations in the crank though (crank twisting itself back and forth while it's spinning due to the power strokes), which is different to the vibration you get from an unbalanced rotating assembly, and you won't have anything to dampen these torsional vibrations if you remove the OEM balancer (unless you fit an ATI or Ross/UAS harmonic balancer).
Yeah my Zed is an auto. Had a short discussion with dad over this as well. He said it like this "Imagine you have your foot on the clutch, and the engine revving hard. Then you let your foot off the clutch.. and because you have so many revs built up... and such a light pulley. It's going to put a lot of strain on the pulley and belts all at once." Where as with a heavier pulley, it softens the blow when it takes all the revs at once, because it takes longer to build up momentum.
it's not just power gains though, you are sacrificing torque to make that power which results in the below situation: I ended up keeping my stock balancer. Didn't really need the extra response as the lighter flywheel and bigger throttles had the desired effect I was after. Even with flywheels you don't want to be going too light as you will drop a tonne of torque when you get one of those 5KG flywheels etc.
The UDP I have on order is a GFB one. Would you say that it would be a quality product? I've had a read through 2 zx builds from Zoom magazine and both of them had Ross/UAS harmonic balancers. Are these the way to go?
Can't say I agree with your theory of tranferring vibrations into the softer metal of aluminium but we'll leave that for Todays' Scientest Magazine As for the drive belts, no you need to get longer ones.
you're not shifting fast enough I'm still waiting for evidence on damage done with an alloy pulley (lets not bring inline 6's into this)
I think I asked this question before tho. What will get you going quicker. More torque or more response? seems pretty complex to me Though I imagine there is only so much lightening and response you can get before it becomes a major annoyance to drive everyday.
Bugger... Do you think Cazracing will give me the belts to match? As I did order a 100k service kit with my UDP.. soo it kinda makes sense? I hope they considered that
To get you off the line, torque is life. I had plenty of issues the last time I went to the drags. Conditions were not ideal as it was drizzling on and off but I had more trouble than others getting off the line. Car either spun the wheels too much or bogged down too early. I've always felt Sandeep's car with the stock flywheel was much easier to launch and more consistent but since drags isn't what I modified my car for, I'm keeping the flywheel but can't see the point in making it any worse with UDP as well. My terminal speed was high for a NA and that's where the drivetrain lightening kicks in but off the line, 60' times were rubbish. If you are looking for a noticable response difference, a tiny 0.5kg alloy UDP cannot be compared to the Ross balance which serves a different purpose. They're are only around a kg lighter than stock and marginally smaller in diameter. The main purpose is to improve engine balance where the stock one can't keep up in high hp applications.
It is not too often I flat shift customers cars. They may get upset if it breaks and rolls to a stop just ahead of a couple of big black lines. Rb's seem to blow themselves to bits with an non-dampened pulley, but the vg has a very short stout crank unlike an rb.
No matter how balanced a motor may be vibration is still there due to each combustion stroke of each cylinder, this sends a sudden jolt through the crank and its components the rubber ring in the crank pulley is there to absorb that force That's the same reason why all the manual commodores from the series two VS have a rubber ring on there fly wheel its called a duel mass flywheel and there as useless as t1ts on a bull especially at $1k a pop and have to be replaced every clutch job Joe
If the only issue is that the aftermarket UDP is missing a rubber ring to absorb torsion.. then wouldn't you think.. somewhere along the line companies engineering Under Driven Pulleys would just include a rubber ring to absorb vibration? I mean.. it couldn't have been that hard to implement.. So unless they just didn't notice it or something stupid.. I'd say the reason an aftermarket UDP doesn't have the rubber ring is because it doesn't need it?
Shorter. Smaller diameter calls for shorter belts. Unless you want to go the full kit and oversize all slave pulleys, which I don't think is a healthy idea. I've got the 5kg flywheel and though I've never driven mine with a stock flywheel, I have noticed comparing to other cars that the revs do drop too much during normal driving. So to fix that, I limit normal driving! I'm keen to try a UDP with the flywheel. If I don't like it I can always swap it back.
There good on auto zeds because you don't have to take your foot off the gas to change gear, the engine is revving higher and producing power, so you dont have any noticable torque loss, the engine and turbos responds better atr that time because of the lightened pulley, no so for a manual, for reasons already stated, looses rpm quicker between shifts, and drops of boost at the same time, you need a few more rpm to get moving. I did notice braking improved marginally when i had a udp on my car, and as far as causing vibration, there was none, UR GFB ect udp's don't cause vibration. ,
Well the rubber ring flogs out every now and then and the whole pulley need to be replaced, the only reasons for them not to put one in is possibly the manufacturing costs and that there is no point of failure in the UDP it self. Although if it was me then i would just stay with standard, surly there cant be astronomically huge gains to be had, but then again i have no practical experience with an UDP Joe
Apparently the design engineers at Nissan & virtually every other manufacturer has missed the fact a harmonic balancer is not required! Imagine the cost savings these manufacturers could recoup by eliminating these balancers on every engine they produce, it would amount to millions of dollars! I wonder why they don't do it?
Very well. Well after having such a long lengthy discussion about UDP's I'm convinced that I will install one and it will work awesome on my auto TT. Read some reassuring information off the GFB website in regards to the UDP as well. If anyone is interested in reading some technical information in regards to why UDP's are not bad for your engine then here's a link. http://www.gofastbits.com.au/pulley-kits/pulley-kits
Well. To say the least. I don't think the VG30DETT actually has a Harmonic Balancer. It's internally balanced via the crankshaft, (which is also very stout.) therefore not needing a harmonic balancer unlike inline 6 engines which have a longer crankshaft. The VG30DETT has a Crankshaft Pulley with a Rubber ring to absorb torsion created ONLY from the fact that the crankshaft pulley itself is heavy. The heaviness of the stock Pulley "excites" any vibration already made by the engine, hence why nissan added the rubber ring. On the other hand. A billet cut UDP is only 20% the weight of the stock Crankshaft Pulley or (Harmonic Balancer as you may like to call it.) So therefore it does not "excite" any vibration, as the rotating inertia is reduced. Therefore! Not needing to have a rubber ring like the Heavy Stock Pulley.
